Maxima Function
rncombine (expr)
Transforms expr by combining all terms of expr that have
identical denominators or denominators that differ from each other by
numerical factors only. This is slightly different from the behavior
of combine, which collects terms that have identical denominators.
Setting pfeformat: true and using combine yields results similar
to those that can be obtained with rncombine, but rncombine takes the
additional step of cross-multiplying numerical denominator factors.
This results in neater forms, and the possibility of recognizing some
cancellations.